Entrance doors are mostly made from solid wood, but can also be combined with other materials, such as glass. The wood used for the construction of doors have to be healthy and free from any flaws. Acceptable variations include a slight wine curvature, small knots and alike. The wood has to be of high quality, artificially dried to some 8-10% of moisture. If those conditions have not been met, cracks and splits might occur.
The most commonly used types of wood are oak, beech, cherry or ash, conifers like fir, spruce or pine trees, occasionally mahogany or meranti.
Lately, thermally treated wood is often used, the wood which has been processed in the temperature higher than 190 degrees Celsius, which is proven to have various benefits.